I told DS that when he started using the potty like a "big boy",we would change his crib to a "big boy bed" (toddler bed). After about 2 weeks of talking up how cool a big boy bed was, he used the potty and demanded his big boy bed. He had 4 accidents in the next 2 days, but was totally potty trained after that.
Now I'm trying to talk him into switching to a bunk bed.
We never used food as treats, but my niece used raisins as a bribe for her kids.